Chloride is a molecular form of chlorine where the chlorine ion gains an electron from a metal such as sodium or potassium. Unlike chlorine, which is highly reactive, chloride ions are stable. They are also very soluble in water and remain stable in solution.
In the human body, chloride ions are critical for processing food into energy, are a part of many enzymes, and are also critical in maintaining the proper acidity of body fluids. The amount of chloride ions in the body is controlled by the kidneys.